The present invention relates to the detection and identification of analytes using a portable sensing apparatus. More particularly, the present invention relates to a portable handheld electronic nose (e-nose) device.
An electronic nose is an instrument used to detect vapors or chemical analytes in gases, solutions, and solids. In certain instances, the electronic nose is used to simulate a mammalian olfactory system. In general, an electronic nose is a system having an array of sensors that are used in conjunction with pattern-recognition algorithms. Using the combination of chemical sensors, which produce a fingerprint of the vapor or gas, the recognition algorithms can identify and/or quantify the analytes of interest. The electronic nose is thus capable of recognizing unknown chemical analytes, odors, and vapors.
In practice, an electronic nose is presented with a substance such as an odor or vapor, and the sensor converts the input of the substance into a response, such as an electrical response. The response is then compared to known responses that have been stored previously. By comparing the unique chemical signature of an unknown substance to xe2x80x9csignaturesxe2x80x9d of known substances, the unknown analyte can be determined. A variety of sensors can be used in electronic noses that respond to various classes of gases and odors.
A wide variety of commercial applications are available for electronic noses including, but not limited to, environmental toxicology and remediation, biomedicine, such as microorganism classification or detection, material quality control, food and agricultural products monitoring, heavy industrial manufacturing, ambient air monitoring, worker protection, emissions control, and product quality testing. Many of these applications require a portable device because they are located in the field or because they have an inaccessible location for larger laboratory models. Conventionally, most of the electronic noses have been large cumbersome laboratory models incapable of being used in the field and pilot plant applications. If available, a portable or handheld device would provide the portability required for pilot plant and field locations. Unfortunately, the portable chemical detectors that have been developed thus far have many limitations that have kept them from being widely accepted.
For instance, U.S. Pat. No. 5,356,594, which issued to Neel et al., discloses a portable volatile organic monitoring system designed for use in detecting fugitive emissions. The device includes a bar code reader for inventorying the emission site. The device contains a single sensor responsive to ionized gas, however the device only detects the amount (i.e., concentration) of the volatile compound. The device is incapable of identifying the volatile organic compound. Thus, the device is merely a vapor amount logger and not a portable electronic nose. As such, the user is required to know the identity of the vapor being quantitated or this information must be stored elsewhere.
Another example of a portable device is disclosed in U.S. Pat. No. 4,818,348 issued to Stetter. Although this portable device is more sophisticated than the previous example, it still has many limitations. In this instance, the device is capable of identifying a gas or vapor, but the applications are quite limited because of sensor architectural limitations. The sensors making up the array are permanently fixed, and thus, the number and variety of analytes and gases that the device is capable of identifying is quite small. Moreover, because the analyte or vapor being identified interacts with each sensor of the array in a different amount, the reproducibility and stability of the device is quite limited. These limitations effect the device""s accuracy in identifying unknowns.
In view of the foregoing, there remains a need in the art for an electronic nose that is portable and, in certain instances, handheld. Moreover, a device is needed that is useful in a broad variety of applications and can respond accurately to a broad variety of gases, analytes, and fluids. A vapor-sensing device is needed that is very versatile, stable, and meets the needs of a wide range of industries and users. The present invention fulfills these and other needs.
The invention relates generally to a sensing apparatus (also referred to as an electronic-nose or e-nose device). The apparatus is compact and, in certain embodiments, configured to be a handheld device. The e-nose device can be used to measure or identify one or more analytes in a medium such as vapor, liquid, gas, solid, and others. Some embodiments of the e-nose device includes at least two sensors (i.e., an array of sensors) and, in some other embodiments, about two to about 200 sensors in an array and preferably about four to about 50 sensors in the array.
The e-nose device is versatile and meets the needs of a wide range of applications in various industries. In certain embodiments, the device is designed as a slim handheld, portable device with various functionalities. In another embodiments, the device is designed as a portable field tool with full functionality. The e-nose device typically includes an internal processor for processing samples and reporting data. Optionally, the device can be coupled to a computer, such as a personal computer, for access to set-up and advanced features and for transfer of data files.
In some embodiments, sections of the e-nose device are disposed within modules that can be installed, swapped, and replaced as necessary. For example, the sensor module, sampling wand or nose, battery pack, filter, electronics, and other components, can be modularized, as described below. This modular design increases utility, enhances performance, reduces cost, and provides additional flexibility and other benefits.
A specific embodiment of the invention provides a handheld sensing apparatus that includes a housing, a sensor module, a sample chamber, and an analyzer. The sensor module and the analyzer mount in the housing. The sensor module includes at least two sensors that provide a distinct response to a particular test sample. The sample chamber is defined by the housing or the sensor module, or both, and incorporates an inlet port and an outlet port. The sensors are located within or adjacent to the sample chamber. The analyzer is configured to analyze a particular response from the sensors and to identify or quantify, based on the particular response, analytes within the test sample.
In a variation of the above embodiment, the housing of the handheld sensing apparatus includes a receptacle, and the sensor module is removably mounted in the receptacle of the housing. In this embodiment, the sensor module can include one or more sensors.
Another specific embodiment of the invention provides a sensor module configured for use with a sensing apparatus. The sensor module is disposed within a housing that defines a receptacle. The sensor module includes a casing, a sample chamber, an inlet port, an outlet port, at least two sensors, and an electrical connector. The casing is sized and configured to be received in the receptacle of the sensing apparatus. The inlet port is configured to be releasably engageable with a port connection of the sensing apparatus when the sensor module is received in the receptacle. The inlet port receives a test sample from the sensing apparatus and directs the test sample to the sample chamber. The outlet port is configured to discharge the test sample from the sample chamber. The sensors are located within or adjacent to the sample chamber and are configured to provide a distinct response when exposed to one or more analytes located within the sample chamber. The electrical connector is configured to be releasably engageable with a mating electrical connector of the sensing apparatus when the sensor module is received in the receptacle. The electrical connector transmits the characteristic signals from the sensors to the sensing apparatus.
Yet another specific embodiment of the invention provides a handheld sensing apparatus for measuring the concentration of one or more analytes within a sample chamber. The sensing apparatus includes two or more chemically sensitive resistors, conditioning circuitry, an analog-to-digital converter (ADC), and an analyzer. Each chemically sensitive resistor has a resistance that varies according to a concentration of one or more analytes within the sample chamber. The conditioning circuitry couples to the chemically sensitive resistors and generates an analog signal indicative of the resistance of the resistors. The ADC couples to the conditioning circuitry and provides a digital signal in response to the analog signal. The analyzer couples to the ADC and determines, based on the digital signal, the identity or concentration of the analyte(s) within the sample chamber.
Yet another embodiment of the invention provides a portable, handheld vapor sensing apparatus that includes a sensor module incorporating a plug-in array of vapor sensors that provide different electrical responses to one or more distinct vapors. The apparatus includes a handheld housing, and the sensor module optionally can be removably mounted in a receptacle formed in the housing. The sensor module defines a sample chamber to which the array of vapor sensors is exposed. The sample chamber incorporates a vapor inlet and a vapor outlet, and a pump is mounted within the housing for directing a vapor sample from the vapor inlet through the sample chamber to the vapor outlet. A monitoring device also is mounted within the housing, for monitoring the electrical responses of the array of vapor sensors and for producing a corresponding plurality of sensor signals. In addition, an analyzer is mounted within the housing for analyzing the plurality of sensor signals and to identify any vapor sample directed through the sample chamber by the pump.
In more detailed features of the invention, the handheld vapor sensing apparatus further includes a controller or processor configured to control the pump either to direct one of a plurality of reference vapors or an unknown vapor sample through the sample chamber. When the controller is controlling the pump to direct one of the plurality of reference vapors through the sample chamber, the monitoring device monitors the electrical responses of the array of vapor sensors to produce a reference signature. Thereafter, when the controller is controlling the pump to direct the unknown vapor sample through the sample chamber, the monitoring device monitors the electrical responses of the array of vapor sensors to produce a vapor sample signature. The analyzer then compares the vapor sample signature with a plurality of reference signatures, to identify the unknown vapor sample.
In other more detailed features of the invention, the sample chamber of the handheld vapor sensing apparatus is defined by the sensor module, alone, and it is sealed from the external environment except for the vapor inlet and the vapor outlet. In addition, each sensor module includes a plurality of first electrical connectors and a plurality of devices of substantially identical size and shape, the devices together carrying the array of vapor sensors and each including a second electrical connector along one edge thereof, for mating engagement with one of the first electrical connectors.
In yet further more detailed features of the invention, the handheld vapor sensing apparatus further includes an electrical circuit that controls the temperature of the array of vapor sensors. In addition, when the sensor module is configured to be removably mounted in the housing receptacle, the module carries an identifier for identifying the vapor sensors it carries, and the monitor further is configured to read the identifier carried by the sensor module received in the receptacle.
In an embodiment, the sensors are implemented with chemically sensitive resistors having resistances that vary according to the concentration of one or more prescribed vapors within the sample chamber. These chemically sensitive resistors are each connected in series with a separate reference resistor, between a reference voltage and ground, such that an analog signal is established for each chemically sensitive resistor. An analog-to-digital converter is responsive to these analog signals and to the reference voltage, to produce digital output signals indicative of the resistances of the various chemically sensitive resistors. A multiplexer can be included for sequentially connecting the various analog output signals to the analog-to-digital converter. In addition, an analyzer is responsive to the digital output signals, to determine the presence and/or concentration of one or more prescribed vapors within the sample chamber.
Other features and advantages of the present invention should become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.